1. Field of the Invention
This invention relates to servicing a wellbore. More specifically, it relates to servicing a wellbore with latex cement slurries containing salt and methods of using same.
2. Background of the Invention
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed.
Sealant compositions for use in wellbore servicing may contain modifiers to enhance the mechanical properties of the sealant. Latex emulsions, which may contain a stable water-insoluble, polymeric colloidal suspension in an aqueous solution, are commonly used in sealant compositions to improve the properties of those compositions. For example, latex emulsions are used in cement compositions to reduce the loss of fluid there from and to reduce the cement's permeability to gas thereby substantially increasing the cement's resistance to gas flow from a gas-bearing formation. Latex emulsions are also employed to reduce the brittleness and improve the flexibility of sealant compositions; otherwise, the compositions may shatter under the impacts and shocks generated by drilling and other well operations.
The use of latex emulsions in sealant compositions may have some disadvantages. For example, cement slurries containing a latex emulsion when subjected to a salt solution often coagulate to form a gelled mixture that is unsuitable for use as a sealant composition. Thus, a need exists for salt-water stable cement slurries containing a latex and methods of preparing same.